Annular air hammer apparatus for drilling wells

Abstract

An annular air hammer apparatus for drilling wells has a cylindrical body which accommodates a stepped annular hammer mounted for reciprocations. A stepped air distribution tube is rigidly secured in the body and has inlet ports and exhaust ports, the tube cooperating with the hammer and defining therewith a work stroke chamber and defining a return stroke chamber with the body. A pipe for receiving drillings is stationary mounted in the air distribution tube and defines therewith a plenum. An annular member is provided between the pipe for receiving drillings and air distribution pipe, in the zone between the inlet and exhaust ports, to define an exhaust chamber between the pipe for receiving drillings and air distribution tube. The plenum and exhaust chamber permanently communicate with each other through a throttle means.

What is claimed is: 
     
       1. An annular air hammer apparatus for drilling wells, comprising: a cylindrical body;   a hammer received coaxially for reciprocations from a top position to a lower position in said body;   a stepped air distribution tube rigidly secured in said body and cooperating with said hammer;   a work stroke chamber defined between said air distribution tube and said hammer;   a return stroke chamber defined between said body and said air distribution tube;   a pipe for receiving drillings mounted in stationary disposition in said air distribution tube and having an interior space for the removal of drillings from the well bottom;   a plenum defined between said pipe and said air distribution tube;   a source of a gaseous fluid under pressure;   said plenum having an inlet establishing permanent communication between said plenum and said source of a gaseous fluid under pressure;   admission ports in the upper step of said air distribution tube for alternately communicating said plenum with said return stroke chamber when said hammer is in the lower position;   exhaust ports in the lower step of said air distribution tube;   a rock breaking tool mounted in the lower part of said body for axial movements;   an axial passage in said rock breaking tool, for providing communication between said pipe and the exterior of the hammer apparatus;   blowing passages in said rock breaking tool for feeding the gaseous fluid under pressure to said pipe for receiving drillings and for removing broken rock therethrough to the surface;   an annular member provided between said pipe for receiving drillings and said air distribution tube in the zone between said admission ports and said exhaust ports of the air distribution tube;   an exhaust chamber defined by said annular member between the outer surface of said pipe for receiving drillings and inner surface of said air distribution tube, the exhaust chamber alternately communicating through said exhaust ports of the air distribution tube with said work stroke chamber when the hammer is in the lower position and with said return stroke chamber when the hammer is in the upper position and;   a throttle means provided between said pipe for receiving drillings and said air distribution tube, the throttle means being located below the admission ports, said exhaust chamber permanently communicating with said plenum through the throttle means.   
     
     
       2. An apparatus according to claim 1, wherein the throttle means comprises at least one orifice in said annular member. 
     
     
       3. An apparatus according to claim 1, wherein said annular member comprises a shoulder on the outer periphery of said pipe for receiving drillings. 
     
     
       4. An apparatus according to claim 1, wherein said annular member comprises an inner shoulder of said stepped air distribution tube. 
     
     
       5. An apparatus according to claim 3, wherein said throttle means comprises an annular space defined between the shoulder of said pipe for receiving drillings and inner surface of said air distribution tube. 
     
     
       6. An apparatus according to claim 4, wherein said throttle means comprises an annular space defined between the inner shoulder of said air distribution tube and outer periphery of said pipe for receiving drillings. 
     
     
       7. An apparatus according to claim 1, wherein the total cross-sectional area of said exhaust ports of the air distribution tube and said throttle means is equal to the total cross-sectional area of said blowing passages of the rock breaking tool.